The present invention relates in general to a method and apparatus for spanning operation of a cellular telephone between two cellular systems and in particular to spanning operation of a cellular telephone between a public cellular system for packet data services and an autonomous cellular system for circuit services.
Wireless communications systems come in many xe2x80x9cshapes and sizes.xe2x80x9d Some systems offer exclusively voice services. Other systems offer exclusively data service. Still other systems offer a combination of voice and data services. Typically each system comes with a different set of frequencies in which it operates and a different set of protocols it uses for providing communications on these frequencies. Some of these systems cover large contiguous geographical regions, while others cover small specialized pockets. Still further, the cost of equipment and airtime varies from system to system. In other words, different systems are designed around different performance requirements.
Often the geographical coverage of two or more of these cellular systems will overlap. Accordingly, some cellular telephones are designed to take advantage of more than one system. For example, a cellular phone may communicate with a cellular system under most circumstances, but automatically switch to communicate with a private autonomous transceiver connected to the user""s residential telephone line when he is in his home. This arrangement may decrease operational costs. However, if the user also receives data services with voice services from the cellular system, the data services may be lost when the phone switches to the residential system, because the typical landline phone service does not deliver the same data that a cellular system delivers.
One solution to this problem is a cellular telephone with more than one receiver. Such a phone could continue to monitor the cellular system for data while using the local residential system for voice calls. However, an additional receiver would increase the cost and complexity of the cellular telephone. Another solution is to periodically alternate the tuning of a single receiver between a carrier frequency associated with the residential system and a carrier frequency associated with the cellular system (i.e., frequency hopping). However, this solution is also unsatisfactory, because the data frequencies of the two systems may not allow such carrier frequency hopping without occasionally missing a call and/or some data.
The present invention is directed to a system for spanning operation of a cellular telephone between a public cellular system and an autonomous cellular system. Typically, the geographic region of the autonomous cellular system is within the geographic region covered by the public cellular system. When the cellular telephone is within a region of overlap between the autonomous system and the public system, it may use the public system primarily for data services and the autonomous cellular system for voice services. When the cellular telephone leaves the region of overlap and enters a region covered only by the public system, it may switch to using the public system for both data and voice services.
In one aspect, the invention is directed to a method for spanning operation of a cellular telephone between a public cellular system for packet services and an autonomous cellular system for circuit services. The public cellular system covers a first geographic region and the autonomous cellular system covers a second geographic region, wherein the first geographic region intersects the second geographic region. Using the method, the cellular telephone receives a pointer to a public control channel associated with the public cellular system via an autonomous control channel associated with the autonomous cellular system. The cellular telephone then makes a request for packet service by transmitting an attach message to the public cellular system via the public control channel. If the cellular telephone receives a success message from the public cellular system via the public control channel (e.g., a positive acknowledgment to the attach message), then the cellular telephone makes a request to initiate circuit services by transmitting a first registration message to the autonomous cellular system via the public control channel using a first tunneling protocol. If the cellular telephone receives a circuit page message from the autonomous cellular system via the public control channel using a second tunneling protocol (e.g., a request to accept a pending cellular telephone voice call), then the cellular telephone acknowledges the circuit page message by transmitting a page response message to the autonomous cellular system via the autonomous control channel.
In one embodiment, the cellular telephone makes a request to place a cellular telephone voice call by transmitting an origination message to the autonomous cellular system via the autonomous control channel. In some embodiments, the cellular telephone makes a request to terminate circuit services with the autonomous cellular system by transmitting a de-registration message to the autonomous cellular system via the public control channel using the first tunneling protocol, and the cellular telephone also makes a request to initiate circuit services with the public cellular system by transmitting a second registration message to the public cellular system via the public control channel.
In a preferred embodiment the first geographic region is larger than the second geographic region, and the first geographic region completely encompasses the second geographic region. Further, in a preferred embodiment, the public cellular system is a Global Station for Mobile Communications (GSM) station operating according to the GSM 03.60 GPRS-136 general packet radio service system standard, the public control channel comprises a TIA/EIA-136-123 DCCH Layer 3 digital control channel, and the first tunneling protocol and the second tunneling protocol comprises a TIA/EIA-136-336 TOM protocol.
In another aspect a cellular telephone capable of spanning operation between a public cellular system for packet services and an autonomous cellular system for circuit services is provided. The public cellular system covers a first geographic region and the autonomous cellular system covers a second geographic region. The first geographic region intersecting the second geographic region. The cellular telephone includes a receiver for receiving a pointer message via an autonomous control channel associated with the autonomous cellular system. The pointer message includes a pointer to a public control channel associated with the public cellular system. The receiver also receives a success message from the public cellular system via the public control channel. The success message is indicative of a positive acknowledgment to the attach message. Still further, the receiver receives a circuit page message from the autonomous cellular system via the public control channel using a second tunneling protocol. The circuit page message is indicative of a request to accept a pending cellular telephone voice call. The cellular telephone also includes a transmitter for transmitting an attach message to the public cellular system via the public control channel. The attach message is indicative of a request for packet services. The transmitter also transmits a first registration message to the autonomous cellular system via the public control channel using a first tunneling protocol. The first registration message is indicative of a request to initiate circuit services. Still further, the transmitter transmits a page response message to the autonomous cellular system via the autonomous control channel. The page response message is indicative of a positive acknowledgment to the circuit page message. In addition, the cellular telephone includes a controller. The controller is operatively coupled to the transmitter and the receiver. The controller is adapted to decode the pointer message, decode the success message, decode the circuit page message, generate the attach message, generate the first registration message, and generate the page response message.